Before moving on our discussion on horizontal and vertical genres, let me talk about my experience with an unknown film on TV I saw yesterday (Friday).
Vertical Genre as an Unknown Variable
I dived into the middle of the film, where a woman was being chased by a reaper. She ran into a room, forcefully locked the door behind it to keep the reaper out. Time was running out as the reaper vigorously spins through the locks and handles trying to open the door. The woman desperately opened up the secret door behind a bookshelf and entered the secret room, locked by one or two layers of metal door. She was still nervous, since she still hears the banging sounds made by the reaper.
At this point, I was wondering what the reaper could do. If he's a reaper, he can simply use his magical powers to go through the doors or teleport, or even use a charged magical attack to blow through the doors. It seems it was unlikely. The reaper wore a plastic mask and there was no fog of dust surrounding him. What the reaper can and cannot do depends on the vertical genre of the film, specifically, realistic or urban fantasy. Before I didn't even know the title or the beginning of the film, I couldn't even know its vertical genre at all, so I was confused.
Later on, the reaper reveals to be a guy with costume and voice changer. From the verbal confrontation between the reaper and the woman, I concluded the vertical genre was realism and the horizontal genre was somewhere in revenge and drama.
Then I proceed to dinner, and I began to think, is the vertical genre (or any aspects of it) eligible to be a spoiler: Is there a circumstance where answering "This novel is a science fiction" when someone knows nothing about the novel will spoil the plot? This might happen for a fantasy story that reveals all the magic came from aliens and the world was a space colony being set into a Dark Age.
What do we watch before watching a new film? Trailers. Trailers play a role at revealing the genres, horizontal and vertical, of the film in question, so we know Godzilla (2014) is a science fiction, albeit on the softer side. Watching the film confirms the vertical genre consistency: The giant creatures came from natural evolution rather than Greek mythology being real.
There are other trailers that are unclear about their vertical genres, and even mislead people into confusing a science fiction into fantasy. However, misleading trailers tend to be people on the Internet passing a comedy (horizontal genre) into horror (horizontal genre, often correlated with a non-realistic vertical genre), and it's highly unlikely to pass a film about a Greek war hero into a space opera.
There are works of fiction that actually subvert the vertical genre, intentionally or unintentionally. I played a visual novel called Moe Cure Net. At the time I was buying it, I knew it is a standard BxG plot in a Japanese high school. I also made an implicit assumption that its vertical genre is realism. Somewhere in the story, there was a rumor about ghosts (evil spirits, I forgot). Under my assumption, I didn't take that statement seriously.
Later on in the Yuna route, it turned out Yuna's soul was captured by a Polaroid camera, and how Yuna survived a car crash began to make sense.
In Moe Cure Net's VNDB entry (vndb.org/v8252)
, the visual novel's tags are grouped by spoiler and non-spoiler. The tags are generally not genre classifications, but many of them describe the traits of plot and characters involved, and one of the spoiler tags, Ghost Heroine, reveals the vertical genre of the visual novel, that it's supernatural. Interestingly, the sample Ren'Py visual novel Moonlight Walks also has a girl which will be revealed to be a ghost... on Modern Day Earth.
There are many implications of treating vertical genres as a potentially unknown or varying piece of information. First, changing the vertical genre from realism to speculative opens up potential for pulling a deus ex: Cornered guy suddenly realizing his teleporting ability? Along the line of distinguishing the realistic and speculative, the author can introduce a paranormal experience and allow the reader to interpret as a hallucination or an actual supernatural encounter. Subjective reality do play a role in epistemology, and in vertical genres. Secondly, within the set of speculative fictions, authors can make a point (Clarke's Third Law, for example) or troll the reader by making a science fiction turn out to be fantasy or vice versa. Third and lastly, universe simulations allows a fantasy world to reside within science fiction world, and the existence of the simulation can be public knowledge or spoiler.